yes, you could buy a new scope for $500, but after that it would not have a personality. it would also need upgrades to make it as you wanted it. that said I would think it breaks down to.... do you like working on your equipment? and by the time you got through rebuilding the coulter, you would have spent just as much, maybe more, but you would have a unique, PREMIUM scope.
also during the time of rebuilding you will be able to use it. spending money in smaller amounts at a time, instead of one large lump sum, and then spending smaller amounts anyway, for upgrades. is not the enjoyment of spending time on your scope worth something?

I like personalized stuff. it tells something about one.
I would go for the rebuild. and when I was done , show the person that you got it from , what he might have done.

Theo